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Old 03-24-2008, 11:30 AM   #1 (permalink)
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Help! Tire has "flat spots" -- Any advice?

My new exige has a pretty bad shimmy whenever I go faster than 60-65 mph. After taking it into the dealer, this is apparently because my tires have "flat spots" after being stationary for too long (i.e., no one drove it at the dealership for a number of months). They suggested that I might be able to simply "drive it off". My car is at about 900 miles right now, so I would have expected for the tires to have been broken in by now.

Does anyone have any advice/comments? Equally important, would attempting to "drive it off" potentially damage my suspension or anything else in any way?

Thanks!
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Old 03-24-2008, 11:34 AM   #2 (permalink)
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tire warranty?
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Old 03-24-2008, 11:35 AM   #3 (permalink)
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Quote:
Originally Posted by zerok00l View Post
my tires have "flat spots" after being stationary for too long (i.e., no one drove it at the dealership for a number of months). They suggested that I might be able to simply "drive it off". My car is at about 900 miles right now, so I would have expected for the tires to have been broken in by now.
Best bet is to go on a nice curvy road to get the tire up to temperature. When they warm up, any residual flat spotting from sitting should go away. But if it's still there after 900 miles, it might not get better.

It could also be something else, especially if you don't feel it until you are at speed. "Flat spotted" tires should be "bumping" all the time, not just at speed. I'd be more suspicions of out of balance tires - that often doesn't show up until the dynamics start maxing things out at speed.
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Old 03-24-2008, 11:46 AM   #4 (permalink)
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Like Tim says, you can feel flat spots even at low speed. It's a straight up and down bumping feel. Shimmying suggets alignment issues to me. Modern tires come back to their round shape very quickly after sitting once they're warmed up.

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Old 03-24-2008, 11:53 AM   #5 (permalink)
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A048 tires, if they're "out of round" aren't going to come back into shape. I'm not talking about flat spotting from sitting too long, I'm talking about actually being out of round. Mine were.

After two different attempts at alignment, removing remounting and rebalancing the tires, my shimmy was still there. On the third attempt I watched over the tech's shoulder as he was spin-balancing the wheel/tire assemblies, and was suprised to see the quite obvious variation in runout at the tread surface. I was the first to notice it.

Putting Toyo tires on my car cured my shimmy.

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Old 03-24-2008, 11:55 AM   #6 (permalink)
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I think you inadvertently used the wrong title for the thread.
You have a shimmy at speed on a new vehicle - which may (but probably isn't) caused by flat spots.
Therefore you have a straightforward warranty issue....
The quicker you get it back - the less likely things could be clouded by questions about how you've driven it (over potholes etc.)

LT is a great resource for seeing beyond dealers' platitudes....
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Old 03-24-2008, 12:00 PM   #7 (permalink)
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Quote:
Originally Posted by xtn View Post
A048 tires, if they're "out of round" aren't going to come back into shape. I'm not talking about flat spotting from sitting too long, I'm talking about actually being out of round. Mine were.
There's also "flat spotting" from braking/skidding the wheels. When you "grind off" a patch of rubber, it's never going to get back to normal. But with the ABS this shouldn't be a problem with our cars.

Flat spotting from sitting is completely different from being out of round.
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Old 03-24-2008, 12:01 PM   #8 (permalink)
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somewhat common... and a few new cars do not sell because of this issue.

typically new tires (by tire yoko warranty) solve it. proper balancing of the new tires can be an issue.
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Old 03-24-2008, 12:02 PM   #9 (permalink)
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Thanks for the quick responses!

I haven't looked into the tire warranty, but it is a brand new vehicle so I would assume it would be covered one way or another.

Supposedly the dealer already performed a balance and alignment when I took it into the shop a few days ago. (And this thread aside, I would have no reason to believe that they did not do it.) Two people from the service department at Lotus of Atlanta actually rode in the car and confirmed that the shimmy is pretty significant.

This might be a silly question, but should the purported flat spots be apparant to me after a visible inspection?

And should I be worried if they have done already performed a balance/allignment but it feels exactly the same?

Any more advice is appreciated.
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Old 03-24-2008, 12:07 PM   #10 (permalink)
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Apparently, not only did I incorrectly title the thread, but I also researched the incorrect issue (ie, did not look into the shimmy on new vehicles).

Any more information on the potential warranty issues or your past experiences will be useful, as I plan on simply printing this thread out and taking it to the dealer.
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Old 03-24-2008, 12:08 PM   #11 (permalink)
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According to the Yokohama rep, the A048s and AD07s can both be permanently flat spotted by being exposed to cold temperatures while bearing the weight of the car. I was told that once the tires get below about 18 degrees that the physical properties of the rubber will change and the flat spots may not necessarily go away even after being brought back up to temp.

Did your dealer store the car outside during some cold weather?
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Old 03-24-2008, 12:12 PM   #12 (permalink)
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tandemracer:

Very interesting information.

Apparently my car was kept outside up north for a number of months... and looking at the temperature records for the area, frequently got colder than 20 degrees.

Maybe that is the culprit? It would certainly mesh with the fact that my car was balanced/alligned but still has the shimmy.
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Old 03-24-2008, 12:24 PM   #13 (permalink)
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I also had a really bad shake at speeds around 65.

Inflating tire to correct psi helped, but the shake completly dissappeared when I got a new pair of rear tires!


2006 na exige

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Old 03-24-2008, 12:39 PM   #14 (permalink)
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Quote:
Originally Posted by zerok00l View Post
Supposedly the dealer already performed a balance and alignment when I took it into the shop a few days ago. (And this thread aside, I would have no reason to believe that they did not do it.)
Just because they did a tire balance doesn't mean they did it right. Typical tire balancing is done to a spec that is "close enough" (say a 1/4 ounce of weight or so) - this works from most cars, but the lighter a car is, and the less unsprung weight there is (tire/wheel/suspension components) the more the balancing becomes critical.

The more accurately you try to balance a tire, the longer it takes to do the job. Most shops get it "close enough". Close enough for an Explorer isn't close enough for an Elise.

As an example, in my old Elan, I always had a shimmy. Until I took it to a shop owned by and old man that was a perfectionist. He balanced my tires as close to perfect as it could possibly be, and there was absolute no shimmy. This was after several attempts to balance the tires using "computerized balancers".

Early Miatas also have a problem with being very sensitive to wheel balance, getting a shimmy around 60 MPH (it tends to go away by 70 or so) due to out of balance tires.

Quote:
Originally Posted by zerok00l View Post
This might be a silly question, but should the purported flat spots be apparent to me after a visible inspection?
Not silly at all. But you aren't going to see a flat spot unless the tire is spinning on a machine - just looking at it isn't going to notice it being a couple of thousandths out of shape.

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Originally Posted by zerok00l View Post
And should I be worried if they have done already performed a balance/alignment but it feels exactly the same?
Not worried. But they should do a better job, or find a shop that can do a better job. There is a particular machine called a "Road Force" balancer that does a good job on hard to balance tires/cars. It applies a rolling force to the tire as it would experience when it's running on the ground. They are purported to solve problems that other machines can't fix.


Quote:
Originally Posted by tandemracer View Post
According to the Yokohama rep, the A048s and AD07s can both be permanently flat spotted by being exposed to cold temperatures while bearing the weight of the car. I was told that once the tires get below about 18 degrees that the physical properties of the rubber will change and the flat spots may not necessarily go away even after being brought back up to temp.
Yes and no. The real problem is that if you attempt to use the tire when it's cold and deformed, it will have a problem - cracking the internal sidewall structure and such.

They've later alluded to the fact that the car just sitting on the tires (car not being used) won't really do any damage.
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Old 03-24-2008, 12:39 PM   #15 (permalink)
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Old 03-24-2008, 01:02 PM   #16 (permalink)
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Good info on the tire temp issue:

Tire Rack Speaks on 14F Temp Issue

It's always a good idea to put your location down.
People sometimes look at that before offering advice.
You may also find another owner nearby who may offer some help.
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Old 03-24-2008, 01:49 PM   #17 (permalink)
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You can visually check the front tires for flat spots while they are on the car by jacking up and spinning one of the front wheels at a time by hand. Jack up the wheel just enough to clear the ground and give the wheel a good spin with your hands. Watch the tread of the tire and if the tire is out of round the tread will appear to move up and down as the wheel spins. If it is close enough to the ground you will hear the tread scrape the ground every time a high spot goes by.

Unfortunately our tires tend to go out of round with age, and can get to the point where they get so much run out that they can't be balanced and made to run smoothly again. It is also possible to shave the high spots off of out of round tires (it was a somewhat common practice in the old days of bias ply tires) using a large tire shaving lathe, but I am not sure if this is a good idea with modern tires and I haven't seen one of these machines in years.
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Old 03-24-2008, 08:17 PM   #18 (permalink)
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changing wheels (& balancing) with same front AO48s tires didn't help either. I'm going to try a different tire when these wear out...maybe those Bridgestone Potenza re55s tires that aren't sold in US.

http://www.bridgestone.co.jp/tire/po...55s/index.html
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Old 03-25-2008, 08:07 AM   #19 (permalink)
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I agree that it's likely a balancing issue.

One of my A048s had rubber particles (tiny round balls) in it, which made noise when bouncing the wheel/tire on the ground. They may have been part of the molding process; don't know. But, once these were removed, the tire could be perfectly balanced.
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